This invention relates in general to sewing machines and in particular to a new and useful sewing machine having a magazine containing a plurality of separate thread supply needles in needle holders which may be selectively coupled and decoupled to a needle bar.
A thread changing mechanism is disclosed in the German OS No. 29 27 142. This mechanism, intended for small embroidering machines having a plurality of needle bars, provides for each needle bar a magazine which is displaceable in its longitudinal direction, transversely to the longitudinal axis of the needle bar. The magazine accommodates a plurality of needle holders, each carrying a needle, with only one of these holders of the magazine being operable to the needle bar at a time. To change the thread, the embroidering machine must be stopped and the needle bar is lifted above its upper dead center position, whereby the needle holder just connected to the needle bar is retracted into its magazine and thereby uncoupled from the needle bar. As soon as needle bar at the end of this lifting motion has entirely been withdrawn from the magazine, the magazine is displaced and the next needle holder needed for the embroidering operation is brought into a standby position. The needle bar is then lowered again whereby it is coupled to the new needle holder.
Since the regular working stroke of the needle bar is extended by the additional lifting, the total height of displacement is relatively very large and requires correspondingly spaced apart bearings. Further, since another drive, different from the normal one for the working stroke, is needed for the additional lifting of the needle bar, the supporting structure of the needle drive enlarges to dimensions which call for an accommodating housing correspondingly voluminous. This does not raise problems in a development of an embroidering machine, where the size of the housing can easily be adapted. Great difficulties would be encountered however, with an attempt to proceed similarly in connection with a conventional sewing machine.